DPI is not a quality metric of your image. Its purely a conversion factor. It can be used as a way to do rough, estimates of visual quality but only if:
- The DPI is set correctly (72dpi generally means not set at all, important to be careful with this value)
- The average viewing distance is known
- Printing method is known
Now DPI and size of print have a relationship. Therefore having a target size and pixel size leads implicitly to DPI. In this case you DPI is actually 78 in one direction and 73 in the other. Obviously you don't need the picture to stretch on the entire canvas so you have some leeway on the subject.
Is this enough? Well it is a bit on the lower side of low. But that's all you've got. The rule of thumb is to aim at 150 dpi for the size. So your image is about half whats needed in both directions. But id say 90 could be passable. 72 is a bit pushing it. But might be not so bad.Nowhere near perfect for sure.